[Coco] Coco sound 6 bit Dac

Simon Jonassen simon at roust-it.dk
Mon Nov 7 17:21:44 EST 2016

@robert gualt...

PLAY uses the 1bit output afaik.... so not a good DAC tutorial

Just my 2c

/Simon :-)

-----Oprindelig meddelelse-----
Fra: Coco [mailto:coco-bounces at maltedmedia.com] På vegne af Robert Gault
Sendt: 7. november 2016 22:38
Til: CoCoList for Color Computer Enthusiasts
Emne: Re: [Coco] Coco sound 6 bit Dac

Sandrus Magister wrote:
> Hey guys,
> Please can you point me to some information/site on how the 6 bit DAC
> works, how to program it? I would like to write a (simple) sound/music
> player for my game. I have experience with 6809 assembly.
> Just out of curiosity, can I have 3 2-bit channels?
> Cheers
> SM


You are getting into deep waters :) but a good starting point would be to 
examine the Basic PLAY command at $9A22 in the Extended Basic ROM. You can find 
that documented in the Spectral Associates "Extended Color Basic v2.0".
That is on the Internet in various places including,

You will also want to look at a Coco service manual. Regardless of your model, 
the Coco3 service manual (should also be at the Color Computer Archive) has a 
description of the DAC pins at $FF20 and a discussion of the DAC circuitry p. 42.

There were several programs doing what you want published in Coco magazines. You 
may be able to fine those to see how others handled this project.

The circuitry will not support 3, 2-bit channels as such but, as a chord is no 
different from a single note when you look at the waveform, just send the 
combined channels to the DAC.

Slightly off topic but about sound and the Coco DAC was an article I wrote for 
the CoCoNuts news letter, vol.3 issue2.


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